Catherine Mulholland, a historian whose biography of her grandfather William Mulholland sought to correct the image of the man who was sometimes vilified for his central role in bringing water to Southern California, died of natural causes Wednesday at her Camarillo home. She was 88 and had been in decline for several months, her family said.

Mulholland was one of the last two grandchildren of the rugged Irish immigrant who oversaw the construction of the 230-mile aqueduct that carries water from the Owens Valley to Los Angeles. It is one of the greatest engineering feats of the 20th century and a continuing source of controversy for the water wars it provoked.

In high school, a teacher suggested that Mulholland read what historian Carey McWilliams and other writers had said about her grandfather. She was "sobered and perplexed" by their accounts, which cast him as one of the "exploitative overlords" of Southern California.

Probing forgotten records and family memories of a past that she said haunted her for years, she wrote "William Mulholland and the Rise of Los Angeles" (2000) to provide what she believed was a fairer, more nuanced view of the family patriarch, a ditch tender who rose to chief of what is now the Los Angeles Department of Water and Power.

William Mulholland, she said, had been "falsely accused of conspiring with vested interests in the San Fernando Valley in building the aqueduct." She portrayed him as a "pragmatic progressive" who was driven by a vision of public works for the greatest public good.

Securing the region's water future with the 1913 opening of the aqueduct made him such a hero that local leaders named a road after him — Mulholland Drive, which runs along the crest of the Santa Monica Mountains.

He was not beloved in other parts of the state, where farmers and other residents believed they had been swindled out of a precious resource.

The water engineer's career ended in infamy when another of his projects, the St. Francis Dam northeast of Castaic, collapsed in 1928, killing more than 400 people in the worst manmade disaster in California's history. Although the cause of the collapse was not clear, he accepted the blame and died a dispirited and silent man several years later.

History was not kind to him in the ensuring decades. From historians such as McWilliams to the 1974 film "Chinatown," he was portrayed as a figure ensnared in a conspiracy to steal water from the hapless residents of Owens Valley. The movie was loosely based on actual events but became so widely accepted as fact that strangers meeting his granddaughter would react by calling her "Mrs. Mulwray." In the film, Hollis Mulwray was the water department's chief engineer.

She conceived the book after moving back to the San Fernando Valley from the Bay Area in the late 1970s after an absence of several decades initiated in part out of a desire to distance herself from a complicated family history.

Born in Los Angeles on April 8, 1923, she grew up on the 600-acre Mulholland family ranch in the west San Fernando Valley with mother, Addie, the daughter of Calabasas homesteaders, and father, Perry, who was William's oldest son. She said her parents' desire for the best education made her an academic vagabond. She attended at least three different elementary schools before going to North Hollywood Junior High School and Marlborough School for Girls. She graduated from Canoga Park High School in 1940.

Writing in The Times in 1999, she said that when she left home to attend UC Berkeley she "welcomed the anonymity of a place where my name had no particular significance."

She had a bohemian urge for experiences at odds with her background. During a break from college to recover from an illness, she moved back to Los Angeles and convinced her parents to let her study musical improvisation with Lloyd Reese, a master jazz teacher. Reese's connections led her to a lifelong friendship with Charles Mingus, who was destined to become a legendary bassist and composer.

Under their tutelage, Mulholland explored the jazz haunts of Central Avenue and came to understand the racial restrictions of the time. She had long conversations about life and music with Mingus, who was black, but their talks usually took place "on the streets of East Los Angeles in the front seat of my mother's car (the only place we felt an interracial pair could safely talk without being rousted by a cop)," she recalled in 1999.

An English major, she earned a bachelor's degree from UC Berkeley in 1945 and a master's from Columbia University in 1947. She returned to Berkeley for postgraduate work and became friends with some of the era's leading avant-garde poets and writers, including Allen Ginsberg and Jack Kerouac. She had a brief romance with San Francisco Renaissance poet Jack Spicer before marrying Gerard T. Hurley, an English professor, in 1949.

She and Hurley divorced in 1976. She is survived by three children: William, of Richmond, Calif.; James, of Pensacola, Fla.; and a daughter, Catherine Hawkins, of Pebble Beach, Calif.

In the mid-1950s she wrote a play about her early years, "A Wedding in the Valley," which won a Phelan Award for artistic work by Californians.

After the divorce, Mulholland moved back to Southern California and discovered that the "quaint little western villages" that had made up the San Fernando Valley of her childhood had been paved over and "uglified." A Kmart occupied the land where her home had stood. The loss of personal landmarks — ironically, because of development made possible by her grandfather's importation of water from the north — impelled Mulholland to become a historian.

She told the history of her mother's family in her first book, "Calabasas Girls" (1976). Next she chronicled the rise of Owensmouth, the dusty town that grew into Canoga Park, in "The Owensmouth Baby: The Making of a San Fernando Valley Town" (1987).

When Mulholland decided to tackle her grandfather's story, she knew critics would question her objectivity. The story was one "with which in a sense I have lived all my life and which even now may be disbelieved," she wrote, "so fixed in some minds is the certainty of what transpired that nothing would alter their opinion. "

Reviews were mixed. Ben Ehrenreich, writing in L.A. Weekly, said "William Mulholland and the Rise of Los Angeles" offered "few deep insights into either of its subjects, but rather expends most of its energy laboriously, and at times disingenuously, refuting the various conspiracy theories surrounding the city's purchase of Owens Valley land and the construction of the Los Angeles aqueduct."

Writing in the Los Angeles Times, Jonathan Kirsch said the book told "a saga of truly heroic proportions … with both grace and grandeur," while the New York Times called it an "even-toned biography" drawn from extensive sources, which included the water chief's personal office files.

"She was an excellent historian," said Abraham Hoffman, a Los Angeles Valley College professor who has written about the water wars between Owens Valley and Los Angeles. "Some people … anticipated that she was going to do some whitewash of her grandfather. She did warts and all. The level of her research went far beyond what anyone else had done on the topic."

Some of the most poignant moments in her account came during her description of the St. Francis Dam disaster and aftermath. The flood raged for 54 miles through Ventura County agricultural communities, ending when it reached the Pacific Ocean. The official death toll was 450, but historians suspected that the number was much higher because hundreds of migrant workers may have been uncounted.

At the time authorities believed the dam broke because it had been built on the San Francisquito fault. Today, experts say the probable cause was a prehistoric landslide that could not have been detected with the limited knowledge of geology in the 1920s.

When the senior Mulholland learned of the collapse, his granddaughter later reported, the first words he uttered were, "Please, God, don't let people be killed." During testimony at one of the hearings on the disaster, he sobbed and said he envied the dead.

Mulholland was only 5 when the dam broke, but she remembered how the accident drained her grandfather's spirit.

She also remembered an incident from a vacation some time later, when her father ran over a water hydrant with the family car, causing a gusher. He ran for help, leaving his father alone beside the shooting stream.

"Only the excitement and confusion of the scene registered on me then," Mulholland wrote, "but now, years later, the memory of that old man who had been one of the world's leading hydraulic engineers standing helpless by a broken water pipe outside a tourist cabin in the desert strikes me as one of those consummately ironic moments when the gods play their Olympian jokes and laugh in heartless derision at us mere mortals." He died in 1935 after a stroke.

Mulholland, who lived in Chatsworth for many years before moving to Camarillo in 2007, spent her last decades writing and lecturing about her grandfather. She was active on the board of Los Angeles Water and Power Associates, which promotes public education about water issues.